Efficiency of Local Lesion Formation and Multiplication of Tobacco Mosaic Virus Strains in the Inoculated Leaves of Some Host Plants

Abstract

Efficiencies of local lesion formation on the inoculated leaves of some local lesion hosts were compared among tobacco mosaic virus (TMV) ordinary strain (OM), tomato strain (T), and mild strain (3III). Purified viruses and their RNA's of these strains in the same optical density (260mμ) units were compared, using half-leaf method. In number of local lesions on Nicotiana glutinosa, purified virus of T strain induced 50-60% of that of OM strain, while on Datura tatula and Chenopodium amaranticolor it induced about 70% of that of OM strain. Strain 3III also induced 50-60% of OM strain in number of local lesions on N. glutinosa. The viral RNA of T strain obtained by phenol treatment showed lower efficiency of local lesion formation than that of OM strain on N. glutinosa. Sedimentation profiles of viruses and RNA's of T and OM strains in sucrose density-gradient centrifugation were almost similar, respectively, and the peak fraction of the virus and RNA of T strain indicated lower efficiency of local lesion formation than those of OM strain on N. glutinosa and Xanthi nc tobacco.
Multiplication of virus strains in the inoculated leaves of Xanthi tobacco, tomato (cv. Hikari), and Physalis floridana were compared between OM and T strains, with infectivity assay using half-leaf method on N. glutinosa. Considering the efficiency of local lesion formation, the number of local lesions of OM strain were corrected by a factor 0.6.
The inoculum of 0.5mg/ml of T strain showed saturation of infection sites when inoculated on the Xanthi tobacco leaf, similar to the case of OM strain reported by Kubo (1966). Therefore, 0.5mg/ml of virus inoculum was used throughout the experiment. In Xanthi tobacco leaf, the multiplication of OM strain was superior to T strain, while in tomato leaf, T strain exceeded OM strain. In the inoculated leaf disk of Physalis floridana floated on water, difference in multiplication of these two strains was not significant.